A current liquid crystal display element has used a liquid crystal alignment film which has been subjected to an alignment treatment in order to make the liquid crystal uniformly aligned, except for some elements such as a polymer dispersed liquid crystal (PDLC) (Non-Patent Literature 1). The alignment treatment of the liquid crystal alignment film has had, after the liquid crystal alignment film is applied, a process generally called a rubbing treatment, that is, a process for rubbing a film surface with a roller having cloth wrapped around. However, since the process is the step of rubbing the film surface physically, scratches and/or shavings due to the rubbing process deteriorate display performance of a liquid crystal display element disadvantageously. Further, this alignment treatment needs to go through many steps such as a liquid crystal alignment film formation step, a liquid crystal alignment treatment step, and a liquid crystal alignment film cleaning step, thereby complicating the manufacturing process.
Therefore, in view of process and cost, it is largely advantageous to manufacture a liquid crystal cell capable of controlling orientation of a liquid crystal without the liquid crystal alignment film.
Meanwhile, a diffraction grating, which is capable of branch of a light wave, conversion of a propagation direction, condensing dispersion, or the like, has been widely used as a passive element in an optical electronics field such as optical recording or optical information transmission.
A typical manufacturing method is a method using a photoresist used for forming a semiconductor integrated circuit or the like. However, a diffraction element formed in this way has no optical anisotropy, or does not easily form periodic optical anisotropy controlled, and thus cannot control a polarization state. In order to control polarization, it is necessary to control optical anisotropy highly, and to form a structure having periodicity. Therefore, for example, it has been proposed to utilize an axis-selective photoreaction of polyvinyl cinnamate (PVCi) or azobenzene capable of generating optical anisotropy simultaneously when change in a refractive index is caused by a photochemical reaction.
However, birefringence induced in the axis-selective photoreaction of PVCi is as very small as 0.01. Also in azobenzene, large birefringence is not induced. Since characteristics are changed by an external field such as heat or light, or since light absorption occurs in a visible region, it is difficult to apply PVCi or azobenzene to a passive optical device, which requires high stability.
More, in recent years, realization of a polarization control type diffraction element capable of controlling diffraction characteristics by an electric field has been expected. It is disclosed (Patent Literature 1) that an optical diffraction liquid crystal element characterized by including a polymerization layer having a periodically varying and fixed molecular orientation structure and a low molecular liquid crystal layer. If an orientation state of a liquid crystal can be controlled arbitrarily in a liquid crystal bulk, various optical elements, for example, a diffraction grating having a periodic orientation distribution, a lens, a mirror, and the like can be provided (Non-Patent Literature 2 or 3). However, in a case of the diffraction grating of the structure, in forming a polymerization layer having a molecular orientation structure, it is necessary to perform an alignment treatment, and manufacturing of the diffraction grating is complicated disadvantageously.